A witness at the impeachment inquiry conducted by House Democrats has disputed the testimony of one of the Democrat’s crucial witnesses.

Andriy Yermak, a top adviser to the Ukrainian president, said top diplomat Gordon Sondland, the U.S. ambassador to the European Union, testified during the inquiry he had spoken to him privately, after a meeting in Warsaw on Sept. 1. The meeting between  U.S. Vice President Pence and Ukrainian President Zelenskiy was a part of an ongoing public relations effort to improve ties between the two countries.

Yermak contradicted Sondland’s testimony, claiming there was no private exchange between the two of them.

“I told Mr. Yermak that I believed that the resumption of U.S. aid would likely not occur until Ukraine took some kind of action on the public statement that we had been discussing for many weeks,” Sondland testified.

The ‘statement’ Sondland was referring to allegedly concerned two investigations—one into discredited claims that Ukraine had helped Hilary Clinton in the 2016 U.S. elections, and the other into business dealings in Burisma by former Vice President Joe Biden’s son, Hunter.

“Following this meeting, Ambassador Sondland pulled aside President Zelenskiy’s adviser, Mr. Yermak, to explain that the hold on security assistance was conditioned on the public announcement of the Burisma/Biden and the 2016 election interference investigations,” the report states.

Sondland’s testimony formed a large part of the final report from the House Committee; his testimony was a crucial link in the chain of the impeachment process, the supposed conversation he had with Yermak was the only known point where an American official spoke to a Ukrainian official on any suggestion of a “quid pro quo.”

“Listen, I want to tell you straight,” Yermak told TIME in the interview on Dec. 4, in the first open discussion he has held since the inquiry. “Of course, now, when I watch these shows on television, my name often comes up, and I see people there whom I recognize, whom I met and know,” he said, referring to the witness testimony. “That is their personal opinion, especially the positions they expressed while under oath. I have my own truth. I know what I know.”

“Gordon and I were never alone together,” he said when TIME asked about the Warsaw meeting. “We bumped into each other in the hallway next to the escalator, as I was walking out.”

“And I remember—everything is fine with my memory—we talked about how well the meeting went. That’s all we talked about,” Yermak said.

“I remember very clearly what I said, what I did, and whom I wrote to. I can tell you 100%, and I can answer for this, that everything I did was right. Everything I did was within the law, and I never crossed the line, never violated legal norms or moral ones,” Yermak told TIME.

In a statement, Sondland’s lawyer said: “Ambassador Sondland stands by his prior testimony and will not comment further.”